In treatment of flue gas, dry flue gas desulfurization (DFGD) systems are known. In DFGD processes, lime (CaO) is first converted to hydrated lime (Ca(OH)2) before being placed in contact with the flue gas to be treated. The hydrated lime is placed in contact with the flue gas as a dry or moistened powder within a circulating dry scrubber (CDS) DFGD system. An example of such a CDS DFGD system is the ALSTOM NID™ system (ALSTOM Power Inc., Paris, France) (NID).
WO 97/37747, invented by Stefan Ahman et al., discloses a device for a CDS DFGD system useful for discharging and distributing an absorbent material in a flue gas duct. Accordingly, in a vertical flue gas duct for flue gases containing gaseous pollutants, a discharging and distributing device is arranged to discharge and distribute a particulate absorbent material reactive with the gaseous pollutants in the flue gas to convert the gaseous pollutants to a separable dust.
While methods and equipment capable of removing both particulate and gaseous pollutants from a flue gas stream exist, there remains a need for improved DFGD methods and equipment that operate under low load conditions while maintaining system stability, efficiency and effectiveness.